"It seems like it's a momentum thing if the other team scores early in the game like that and it's tough to come back," Happ said. "Getting out of something like that shifts the momentum and all of a sudden we put something on the board like that. It's definitely big."
Happ (3-3) had allowed 10 earned runs in 10 innings in his previous two starts and hadn't allowed fewer than two earned runs in any of his previous seven starts. It's only the second time in his last 37 starts that Happ has allowed no earned runs and pitched at least six innings.
"We were talking before the game about Happ, wanting to get him back to how he threw the first two or three outings, and he definitely did that today," Astros manager Brad Mills said. "He went out there and was able to execute a plan and try a few different things."
By sweeping the two-game series from the Brewers, the Astros head into this weekend's Lone Star Series against the Texas Rangers and the start of Interleague Play with some momentum and will send ace Wandy Rodriguez to the mound in Friday's series opener.
"You get home and just want to play good baseball and the guys were able to do that," Mills said.
The Astros sent nine batters to the plate in the fourth inning against Brewers starter Shaun Marcum (2-2) and scored four runs, keyed by a two-run home run by Jed Lowrie on a 3-2 fastball he drove down the right-field line to make it 2-0.
"With a guy like that, you have to trust what you're seeing because you have so many different pitches and he really works all of them into the game at some point," Lowrie said. "He's not a guy that's going to rear back and try to throw it by you. You have to see the ball with him. You can't really guess with him because that's when he gets you out."
Marcum said he didn't place the pitch where he wanted.
"It was a fastball that was supposed to be in and came back over the middle third [of the plate]," he said. "When he hit it, I didn't think it was going to be a home run. But unfortunately it went out, and that was all they needed."
The Astros banged out 13 hits -- six in the fourth -- for their highest total in a game since collecting 15 hits on May 2 against the Mets. Houston had gone 12 consecutive games without reaching 10 hits. Jose Altuve had three hits for his 16th multi-hit game, and Jordan Schafer, Chris Johnson and Chris Snyder each had two hits.
"We had a little bit of everybody tonight and it was good," Snyder said. "We scored the four in one inning, and that's all we needed. You've got to love those shutouts."
Mills said Happ did some things different mechanically, but he wouldn't go into specifics. Snyder said Happ went back to what had made him successful in the past, relying on his four-seam fastball -- and not as many cutters -- with an effective changeup and using his curveball to put hitters away.
"When he's forced to do that, that creates more conviction out of him, and it showed tonight," Snyder said. "He had everything working."
Happ also escaped a jam in the fifth inning after the Brewers had runners at second and third with one out. In the sixth, Corey Hart doubled and Jonathan Lucroy singled with one out, but Happ came back to retire Brooks Conrad and Cesar Izturis to preserve the shutout.
"He executed when he absolutely had to and facing some guys who were 100-RBI guys a year in some tough spots and was able to make pitches and get out of tough spots," Lowrie said. "That was really important for us and really important for J.A. to get a little confidence. He did a great job tonight."